In recent years, the recording density of data in a single recording plane is increased in association with increase in capacity of a hard disk or the like in computer equipment. For example, in order to increase the recording capacity per unit area of a magnetic disc, it is necessary to increase the surface recording density. However, in association with increase in recording density, the recording area per one bit on a recording medium is reduced. When the bit size is reduced, the energy possessed by one bit data becomes close to the heat energy of ambient temperatures, and hence a problem of heat demagnetization such as recorded data is inverted or lost due to heat fluctuations or the like arises.
Although a generally used in-plane recording system is a system to record magnetism so as to cause the direction of magnetization to direct toward the in-plane direction of the recording medium, with this system, the above-described loss of the recorded data or the like due to the heat demagnetization is apt to occur. Therefore, in order to solve such inconveniences, it is in the course of transferring to a vertical recording system which records magnetizing signals in the direction vertical to the recording medium. This system is a system in which magnetic data is recorded on the basis of a principle to bring a single magnetic pole to the recording medium. According to this system, a recording magnetic field is directed substantially vertical to a recording film. Data recorded in the vertical magnetic field is easy to maintain its energetic stability since an N-pole and an S-pole can hardly generate a loop in the recording film plane. Therefore, this perpendicular recording system is resistive against the heat demagnetization in comparison with the in-plane recording system.
However, the recording medium in recent years is required to have a higher density in response to a need such that recording and reproduction of a larger amount of higher density data or the like is desired. Therefore, the recording medium having a higher coercivity are started to be employed in order to minimize influences between adjacent magnetic domains or the heat fluctuations. Therefore, even with the above-described perpendicular recording system, recording of data in the recording medium becomes difficult.
Therefore, in order to solve this inconvenience, a hybrid magnetic recording system in which the magnetic domain is locally heated using a spot light obtained by condensing a light or a near field light to lower the coercivity temporarily to allow writing during this period is proposed. In particular when using the near field light, handling of optical data in an area not exceeding the wavelength of the light, which has been considered to be limited in the optical system in the related art, is enabled. Therefore, high-density of a recording bit exceeding the light data recording and reproducing apparatus or the like in the related art is achieved.
Although various types of writing heads on the basis of the hybrid magnetic recording system described above are provided, as one of those, a near field optical head in which heating is performed utilizing the near field light is known (for example, see JP-A-2004-158067 and JP-A-2005-4901).
This near field optical head mainly includes a main magnetic pole, an auxiliary magnetic pole (return pole), a coil winding having a helical conductive pattern formed in the interior of an insulator, a metal scatterer configured to generate a near field light from an irradiated laser beam, a plane laser light source configured to irradiate the metal scatterer with the laser beam, and a lens configured to focus the irradiated laser beam. These respective components are attached to a side surface of a slider fixed to a distal end of the beam.
The main magnetic pole has a surface opposing the recording medium on one end side, and is connected to the auxiliary magnetic pole on the other end side. In other words, the main magnetic pole and the auxiliary magnetic pole constitute a single magnetic poly type vertical head having one magnetic pole (single magnetic pole) arranged in the vertical direction. The coil winding is fixed to the auxiliary magnetic pole in such a manner that part of it passes between the magnetic pole and the auxiliary magnetic pole. The magnetic pole, the auxiliary magnetic pole, and the coil winding as described above constitute an electromagnet as a whole.
The above-described metal scatterer formed of gold or the like is attached to a distal end of the main magnetic pole. The above-described plane laser light source is arranged at a position apart from the metal scatterer and the above-described lens is arranged between the plane laser light source and the metal scatterer.
The respective components as described above are attached in the order of the auxiliary magnetic pole, the coil winding, the main magnetic pole, the metal scatterer, the lens, and the plane laser light source in sequence from the side of the side surface of the slider.
When utilizing the near field optical head configured in this manner, various data are recorded in the recording medium by applying the recording magnetic field simultaneously with the generation of the near field light.
In other words, the laser beam is applied from the plane laser light source. This laser beam is focused by the lens and is applied on the metal scatterer. Then, since free electrons in the interior of the metal scatterer are uniformly oscillated by the electric field of the laser beam, a plasmon is excited so that the near field light is generated at a distal end portion. Consequently, a magnetic recording layer of the recording medium is locally heated by the near field light, and the coercivity is temporarily lowered.
Also, by supplying a drive current to the conductive pattern of the coil winding simultaneously with the above-described laser beam irradiation, the recording magnetic field is locally applied on the magnetic recording layer of the recording medium close to the main magnetic pole. Accordingly, recording of various data in the magnetic recording layer in a state in which the coercivity is temporarily lowered is achieved. In other words, the recording in the recording medium is achieved in cooperation between the near field light and the magnetic field.    [Patent Document 1] JP-A-2004-158067    [Patent Document 2] JP-A-2005-4901